The present invention relates to testing of a radio frequency (RF) data packet signal transceiver, and in particular, to testing such a device for proper implicit beamforming operation.
Many of today's electronic devices use wireless signal technologies for both connectivity and communications purposes. Because wireless devices transmit and receive electromagnetic energy, and because two or more wireless devices have the potential of interfering with the operations of one another by virtue of their signal frequencies and power spectral densities, these devices and their wireless signal technologies must adhere to various wireless signal technology standard specifications.
When designing such wireless devices, engineers take extra care to ensure that such devices will meet or exceed each of their included wireless signal technology prescribed standard-based specifications. Furthermore, when these devices are later being manufactured in quantity, they are tested to ensure that manufacturing defects will not cause improper operation, including their adherence to the included wireless signal technology standard-based specifications.
For testing these devices following their manufacture and assembly, current wireless device test systems typically employ testing subsystems for providing test signals to each device under test (DUT) and analyzing signals received from each DUT. Some subsystems (often referred to as “testers”) include one or more vector signal generators (VSG) for providing the source, or test, signals to be transmitted to the DUT, and one or more vector signal analyzers (VSA) for analyzing signals produced by the DUT. The production of test signals by a VSG and signal analysis performed by a VSA are generally programmable (e.g., through use of an internal programmable controller or an external programmable controller such as a personal computer) so as to allow each to be used for testing a variety of devices for adherence to a variety of wireless signal technology standards with differing frequency ranges, bandwidths and signal modulation characteristics.
Testing of wireless devices typically involves testing of their receiving and transmitting subsystems. The tester will typically send a prescribed sequence of test data packet signals to a DUT, e.g., using different frequencies, power levels, and/or modulation technologies, to determine if the DUT receiving subsystem is operating properly. Similarly, the DUT will send test data packet signals at a variety of frequencies, power levels, and/or modulation technologies to determine if the DUT transmitting subsystem is operating properly.
Current Wi-Fi devices that comply with the IEEE 802.11n standard, as well as some other wireless standards, can employ beamforming as a way to improve range and performance by focusing more signal energy from the device to an access point. When manufacturing such devices, the beamforming capability is tested. One technique includes use of conductive signal paths (e.g., cables to convey the RF signals between the device RF ports and the tester RF ports) to simulate a channel condition that would cause a properly operating device to respond by altering its outputs to beamform the signals being emitted from its RF ports. This response can be detected and measured by the tester signal analysis subsystem(s). However, testing a device using conductive signal paths prevents inclusion of its antenna subsystems as part of the test(s). Thus, such conductive beamforming testing will verify correct operation of a partially assembled device, but will not verify that the fully assembled device (i.e., with its antennas) continues to operate properly.
In order to test a fully assembled device using real-world conditions, one would actually transmit a radiated signal between the antennas of the device and the antenna(s) of a test system. However, doing so within a shielded enclosure to provide isolation from other signals, would place the device in a multipath-rich environment.
Accordingly, it would be desirable to provide a system and method for controlling multipath effects in such a manner that would permit wholly assembled devices, including their antennas, to be tested for beamforming performance in multipath-rich environments with significantly higher degrees of repeatability and accuracy.